There is known a technique in which, in an internal combustion engine which includes a supercharger and which directly injects fuel into a cylinder, causes a valve overlap during supercharging in order to raise temperature of a catalyst and performs stratified combustion while retarding an injection timing of the fuel (for example, refer to Patent Document 1).
In addition, a technique is known which, when a first fuel injection value that injects fuel into a combustion chamber and a second fuel injection value that injects fuel into an intake passage of an internal combustion engine are provided, performs a first temperature raising mode for performing fuel injection by setting an injection timing of the first fuel injection value to a compression stroke and setting an injection timing of the second fuel injection value to an exhaust stroke and a second temperature raising mode for setting the injection timing of the first fuel injection value to the compression stroke and setting the injection timing of the second fuel injection value to an intake stroke for some cylinders and to the exhaust stroke for other cylinders after the first temperature raising mode (for example, refer to Patent Document 2).
Furthermore, a technique is known which, in an internal combustion engine including a supercharger, improves acceleration performance by increasing a valve overlap amount during an accelerating operation to cause intake air to forcibly flow into an exhaust passage, and when subsequently making a transition to a steady operation, reduces a valve overlap while prohibiting a wastegate valve from being driven toward an open-valve side until the valve overlap amount converges to a target value (for example, refer to Patent Document 3).
Moreover, a technique is known for performing fuel injection by a fuel injection valve during a period in which there is a valve overlap, causing a part of the injected fuel to forcibly flow from an intake port to an exhaust port and, accordingly, causing combustion of the forcibly flowed fuel by secondary air while suppressing an air-fuel ratio in a cylinder to a level where misfire does not occur in order to raise exhaust temperature (for example, refer to Patent Document 4).
With an internal combustion engine that performs a lean burn operation, since allowing an overlap to occur causes low-temperature intake air to flow through an exhaust passage, there is a possibility that temperature of a catalyst may drop or a temperature rise of the catalyst may slow down.